<!DOCTYPE html>
<html lang="zh">
	<head>
		<meta charset="utf-8">
		<link rel="stylesheet" href="style.css">
		<title>28 输入框交互</title>
	</head>
	<body>
		<div class="app">
			<label class="label28">
				<span class="span28">用户名</span>
				<input class="inp28" type="text" required>
			</label>
		</div>
	</body>
</html>